Their study showed that hemp hulls had a significant impact on protein digestibility,with dehulled hemp seed having a PDCAAS score of 61%,whereas whole seeds had a score of 51%.This finding could mean that whole seed from hemp lines such as Frog-1 and ECO_50 GC,with high heart %,could have higher protein digestibility,than other lines with similar protein content,but lower heart %.Other possible factors that affect digestibility need to be considered,and these can be evaluated in the future.We demonstrate that the protein is present as protein bodies throughout the seed.To our knowledge this has not been shown before,but is consistent with seed from other dicotyledonous plants.The structure of protein bodies in monocotyledonous seed such as sorghum are known to be formed due to the interaction of several proteins with a hydrophobic protein on the surface of the body.γ-kaffrin is responsible for creating the stable structure of sorghum protein bodies and may impede digestibility.There is no data on the arrangement of the seed storage proteins within hemp seed,but a recent paper has revealed that the C.sativa genome contains six 11S edestin genes,two 2S albumin genes and one 7S vicilin-like gene.There is likely to be variation in the levels of hemp seed storage proteins between genotypes and with environmental conditions which may in turn affect both protein digestibility and the amount of the most limiting amino acid,Lys.A subset of the most promising lines could be analyzed in the future to reveal the extent of genetic variability for specific proteins and bio-availability of Lys.Strong environment and G x E effects on protein content have been shown,P < 0.0001 and P ¼ 0.0019 respectively in a Canadian field trial with 11 lines,although a relatively low CV was obtained for protein in the 20 hemp lines grown in Australia.In the Canadian field trial,the average protein yield for Midlands X,Midlands S and Ferimon 12 ranked 2nd,6th and 7th,with the highest average protein yielding line being FINOLA,at 25.7%,compared to Midlands X,Midlands S and Ferimon 12 at 25.2%,23.8% and 23.0% respectively.In the data reported here,from a single batch of seed,three lines,Ferimon 12,ECO_222 and ECO_208 had highest protein levels at 26.9%,26.2% and 25.9% respectively.Studies in other crops suggest that stress can reduce seed protein content and also change the relative abundance of different storage proteins and amino acid profiles.The relative susceptibility of hemp protein levels and amino acid profiles to environmental factors including heat will be an important area for future selection of hemp lines for food.
The 20 hemp lines analyzed in this study had a greater range of total lipid content,with a higher maximum value of 37.8% ,vertical hydroponic system compared to 34.8% and 30.6% in previous reports.Two of the lines in each of the other studies were also analyzed in this study,Midlands X and Midlands S had slightly higher total lipids in the current study compared to the 2015 report where both lines had 29.5% total lipid.A similar small difference was observed for KC Dora and the 2016 study with 31.5% total lipid,however there was a greater different for Ferimon 12 which had the highest total lipid content in this study at 37.8%,but only 30.2% in Galasso et al..The mean values of the individual lipids are also similar between this study,and the other two studies,with no notable differences.The main benefit of analyzing the individual lipids is to calculate the ratio of omega-6 to omega-3 fatty acids ,which is generally around 3:1 for hemp seed.For example,the twenty lines reported by Galasso and colleagues had a mean LA:ALA ratio of 3.32.Only a single line,CAN24 had a dramatically reduced ratio at 1.63,with the next lowest ratio at 2.63 and another three other lines had a ratio 3.The data reported here revealed that eight lines had LA: ALA 3,with two lines close to 2 and Han-NE.This ratio provides new plant lines to consider in breeding programs to further improve this trait.Lastly,we discuss phytate levels in the 20 hemp lines.Phytate levels in hemp are similar to other oil seeds,most notably,linseed where they range from 2.15 to 3.69 g/100 g.We found three prior hemp studies that measured phytate.The first study obtained a mean value almost 2-fold higher than current study even after taking into account they used defatted flour rather than whole seeds,but the second study had more comparable values at 3.5 0.2 g/100 g.The values reported in our study likely represent real values,as the kit provided oat flour controls gave the expected values,and recovery of total P was as expected for a mixed oat plus hemp control assay compared to the two samples processed individually.Furthermore the mean value reported here of 2.67 0.43 g/100 g is consistent with the value obtained for whole hemp send with a recently “improved” method of phytate determination,of 2.75 g/100 g.Despite the differences in absolute values between this study and Galasso,the samples showed the same trends,with KC Dora having the lowest levels of phytate and Fermion 12 having higher,above average levels of phytate.Phytate is often considered an antinutrient because it can bind/ chelate other nutrients,especially divalent cations ,and affects the bioavailability of micronutrients such as Zn and digestibility of proteins.Another potential negative of high phytate levels is the positive correlation with trypsin inhibitor.This could potentially affect the availability of protein in raw foods,but is not an issue in cooked food.
Phytate does have some positive attributes for human health.It has antioxidant properties and this may in part account for observed anti-cancer activities in,for example,rat studies where pure phytic acid is more efficient at reducing the incidence and growth of mammary tumours compared to all bran.In summary,the new research presented fills some previous knowledge gaps,most significantly providing details on the nature of the major dietary fiber components of hemp seed.The use of antibodies revealed a high level of diversity of polysaccharides and some cell-type specificity for the different plant cell wall polymers.Cellulose and xylan were identifified as the major components of hemp hulls,and hemp hearts contain low levels of starch.The findings contribute to efforts to grow the global hemp industry,especially for food use and to improve human nutrition.Future research into consumer traits is needed,especially in the area of flavour characteristics and new product development.For example,different hemp lines can have different flavour profiles and new products include microgreens,which are excellent ways to reduce anti-nutrients such as phytate and increase antioxidants.With growing worldwide interest in hemp as a more sustainable crop,the breadth of traits incorporated into breeding programs is expected to grow,accelerating the improvement of hemp for consumers and human nutrition.Dispersion of heavy metals in soils is an age-old problem deriving from both natural and anthropic sources.Among the anthropic contribution to soil contamination by metals,land application of treated wastewater,sewage sludge,fertilizers,and industrial activities are major concerns.Unbalanced amounts of heavy metals may cause perturbation of soil parameters with consequent toxic effects on plants,in the nearby water supplies,and,ultimately,in the whole food chain.Typically,elements,such as copper ,nickel ,zinc ,and chromium are biologically essential for plant growth but become toxic for animals and plants when their concentrations exceed certain threshold levels.Other heavy metals often found in contaminated soils,such as cadmium and lead are not essential for plants growth,and many studies associated their presence with neurological and endocrinological toxicity for humans along with carcinogenic effects.Since heavy metals are not biodegradable,they tend to accumulate in the environment becoming a high risk for biota over several years after their introduction in an ecosystem.The search for new solutions that can remediate heavy metals-contaminated soil is a critical prerequisite for the sustainable development of agriculture ,thus representing a topic of paramount importance.
The most consolidated strategies to remediate heavy-metals contaminated soils include physical and chemical approaches,like isolation,through capping and subsurface barriers; immobilization,by solidification/stabilization,vitrification,and chemical treatment; physical separation; extraction,by soil washing,pyrometallurgical extraction,in situ soil flushing,and electrokinetic treatment.Alternative approaches are gaining great attention as they combine cost-effectiveness,sustainability,low toxicity,and mobility decrease.They include bioaccumulation,phytoremediation ,bioleaching,and biochemical processes,in which living organisms such as plants or microbes are used to clean an area from contaminants.In particular,phytoremediation is attracting the attention of the scientific community,since it has been demonstrated to be a costeffective solution for the remediation of contaminated sites,and,in the meanwhile,to be a feasible method for bio-fixation of CO2,resulting in highly sustainable technology.The ability to absorb heavy metals generally depends on the biomass produced as well as on the ability of the plant to accumulate and translocate heavy metals in its biomass.According to recent scientific literature,a good candidate for phytoremediation of heavy metals-contaminated soil is the hemp plant.Kompolti,also known as hemp,the non-psychoactive variety of Cannabis sativa L.,is an annual dioecious high yielding industrial crop,and it is mainly grown for its fibers and seeds and used for textiles,clothing,insulation,biodegradable plastics,food,animal feed,and bio-fuel production.Hemp possesses some characteristics that make it very suitable for phytoremediation,such as high biomass,long roots,and an industrial-favorable short life cycle of 180 days.Importantly,hemp demonstrated a strong capability to sequester heavy metals like cadmium,zinc,lead,nickel,copper,and chromium when are present in contaminated soil and water.Another attractive approach for the remediation of contaminated sites is the application of bioleaching technology which uses direct metabolism or by-products of microbial processes to uptake heavy metals adsorbed onto the soil surface and to transform them so that the elements can be extracted when water is filtered through.Bioleaching has several advantages over conventional physical and chemical strategies,such as low cost,environmental sustainability,low hazardous characteristics of waste/sludge,low energy demand,and absence of toxic chemicals.Besides,phycoremediation,which involves eukariotic algae and cyanobacteria in remediation processes,cannabis grow setup has been extensively applied to the treatment of wastewater.
Nevertheless,its application to the remediation of heavy metals contaminated sediments is less documented.Among the cyanobacteria,Arthrospira platensis possesses excellent chelating properties both towards heavy metals present in humans and towards those present in the soil,water,and sludge.The dried biomass of Arthrospira platensis is commonly known as spirulina and it finds many applications in agriculture as a plant growth promoter,enhancing the growth,increasing the yield,and speeding up the seed germination.Recently,the employment of this blue-green alga to uptake heavy metals in contaminated sites has been explored.The presence of a chloroplast-type ferredoxin in the active center has been reported as responsible for the chelating capability of Spirulina ,whereby its efficiency is affected by many physical and chemical factors such as initial metal concentration,dosage,adsorption time,temperature,and pH.The present study aimed at both exploring the ability of the unreported combined use of hemp and spirulina to uptake six selected heavy metals from artificially contaminated soil and investigating,under controlled plant growing conditions,their distribution into the plant tissues.Specifically,hemp was chosen as the main agent for biological remediation,and spirulina was added as an enhancer of both the plant growth and the translocation of heavy metals in the hemp.The application of a non-targeted Nuclear Magnetic Resonance approach combined with an estimation of the residual metals by Inductively Coupled Plasma Atomic Emission Spectroscopy into the cultivation soil and within the different tissues of the plant was applied in view of gathering useful information on the efficiency of the integrated hemp/spirulina system.Obtaining this information is crucial for the potential re-utilization of the hemp plant or shoots of it,after the phytoremediation stage,for alternative usages,like production of bio-materials for textile industry,constructions,and biofuel.Plants were constantly monitored until the harvest by recording three main morphometric parameters: plant height ,i.e.height of stem from ground to apex,the number of leaf stages,and drum diameter.The biomass of stem and leaf samples was determined upon lyophilization; the sum of the biomass of the stem and leaf samples collected from the same plant was computed too and here referred to as “plant biomass”.The residual amount of heavy metals contained in leaves,stems,and soil after the harvest was measured; for each plant,also the sum of the heavy metal content of leaves plus stems was calculated.The shoots of plants were collected and transferred in refrigerated packaging with dry ice from the greenhouse to laboratories for further analyses.Samples of soil from each pot were collected after harvesting and kept in plastic bags at room temperature until analysis.Leaves and flowers were separated from stems and both portions of the plant were firstly freeze-dried at –50 ◦C and 0.180 mbar for 72 h in a lyophilizer.Then,the dried samples were mechanically ground in a blender,sieved through a mesh with a pore size of 0.5 mm,and stored at –20 ◦C until analysis.